Method and device for manufacturing powder molded body

ABSTRACT

Material powder  17  is filled in a cavity  16  which is composed of a die  12  having a die hole  11  in a shape matching the contour of a green compact and a lower punch  13 . The material powder  17  is temporarily compressed by an upper punch  14  and the lower punch  13  to obtain a preform  18 . A punch-out pin  15   a  is inserted into the preform  18  to punch out a shape of a through-hole  3 . The preform  18  is pressurized and compressed by both of the upper and lower punches  14, 13  to obtain a green compact  19 . The punch-out pin  15   a  is pulled out from the green compact  19  and the green compact  19  is taken out from the cavity  16 . Further, the green compact  19  is sintered and a pair of leg parts  24  connected continuously at a base part  23  and an undercut part  25  between the leg parts  24  are formed by cutting off a part of a peripheral wall  26  of a through-hole  25   a . The punched-out material powder  17  is retracted to and stored in the outside of the cavity  16  and refilled into the through-hole  3  after the punch-out pin  15   a  is pulled out. The material powder  17  is removed after the green compact  19  is taken out.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP00/04825 which has an Internationalfiling date of Jul. 18, 2000, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a manufacturing method and amanufacturing device of a green compact having a through-hole at a partconnected continuously to a base part or a green compact having a pairof leg parts connected continuously at a base part in which a partbetween both leg parts is an undercut part.

BACKGROUND ART

Conventional machine parts include P/M (powder metallurgy) product shownin FIG. 1(a), FIG. 1(b), and FIG. 3(a). The product shown in FIG. 1(a)comprises a rack 2 at an end of a base part 1 and has an axis hole 3penetrating a part connected continuously to the base part 1 formedtherein. The product shown in FIG. 1(b) comprises a hook part 5 at anend of an arm 4 extending from the base part 1 and has the axis hole 3penetrating the part connected continuously to the base part 1 formedtherein.

On the other hand, the product shown in FIG. 3(a) is composed of a hookpart 22 provided at the front end of a rod part 21 and a pair of legparts 24, 24 connected continuously at a base part 23 which is the rearend of the rod part 21, and has an undercut part 25 between the legparts 24, 24.

Methods for manufacturing such a machine part having the axis hole 3 orthe undercut part 25 by P/M include a method in which a green compact ina shape without the axis hole 3 or the undercut part 25 is firstsintered, and then, the axis hole 3 is provided by drilling work or theundercut part 25 is provided by cutting work and the like, and a methodin which the axis hole 3 or the undercut part 25 is provided at the sametime of the powder compaction.

As described in the former method, in a case of performing the drillingwork or the cutting work on the sintered compact, the powder compactingis performed using a die having a die hole in a shape matching thecontour of a desired molded body in a vertical direction and a pair ofpunches inserted into the die hole from the upside and underside of thedie. First, material powder is filled in a cavity which is formed of thedie hole and a lower punch inserted into the die hole from the undersideof the die. Next, the material powder is pressurized and compressed bythe upper and lower punches to a prescribed thickness and the obtainedgreen compact is taken out from the upside of the die hole. The greencompact is sintered, and thereafter, the axis hole 3 is formed by thedrilling work or the undercut part 25 is formed by the cutting work. Inthis method, however, the drilling work or the cutting work istime-consuming and requires an extra cost.

On the other hand, in a case of forming the axis hole 3 or the undercutpart 25 at the same time as the time of powder compacting as describedin the latter method, a powder compacting device is utilized whichcomprises, in addition to the die and the upper and lower punches, ahorizontal punch or a core movable in a direction perpendicular to apressurizing direction for shaping the axis hole 3 or the undercut part25.

As for the powder compacting device comprising the horizontal punch forshaping the axis hole 3 or the undercut part 25, a method is known inwhich the cavity formed of the die hole and the lower punch is filledwith the material powder while being penetrated by the horizontal punch,the material powder is compressed to the prescribed thickness by theupper and lower punches, the horizontal punch is pulled out from theobtained green compact, and the green compact is taken out from theupside of the die hole. In this manufacturing method, since the cavityis filled with the material powder while being penetrated by thehorizontal punch, the material powder is not uniformly filled into alower part than the horizontal punch in the cavity, and it is sometimesimpossible to shape a green compact especially when it has a shape inwhich thickness of a periphery of the axis hole 3 or the undercut part25 (the base part 1 or the leg part 24) is thin.

As for the manufacturing method in which a core in a shape correspondingto the shape of the axis hole 3 or the undercut part 25 is disposed inthe cavity in advance, the cavity with the core disposed therein isfilled with the material powder, the upper punch is inserted underpressure from an opening of the cavity, and the material powder ispressurized and compressed so as to obtain the green compact. The coreis removable from the pressurized and compressed green compact and, bypulling it from the compacted body, the green compact having the axishole 3 or the undercut part 25 can be obtained. In this manufacturingmethod, however, it is difficult to obtain the uniform density of thematerial powder in a lower part and in an upper part than the core whenthe material powder is filled.

Another method is also known in which the cavity formed of the die holeand the lower punch is filled with the material powder, the materialpowder is pressurized and compressed by the upper and lower punches, andthe axis hole 3 or the undercut part 25 is punched out by a punch-outpunch. However, in this manufacturing method, when the green compactobtained by the pressurization and compression is punched out by thepunch-out punch, chipping, breakage or the like may be caused in thegreen compact.

Moreover, if a part of the periphery of the axis hole 3 or the undercutpart 25 (the base part 1 or the leg part 24) becomes thin due to theforming of the axis hole 3 or the undercut part 25 as shown in FIG. 1(b)or FIG. 3(a), both of the manufacturing methods using the core or thepunch-out punch have a disadvantage that breakage may be caused in thethin part when the green compact with the axis hole 3 or the undercutpart 25 formed therein is taken out. In a case in which the undercutpart 25 is formed, there is also a disadvantage that deformation such aswarpage may occur in the leg part 24 in sintering which is performedafter the powder compaction.

DISCLOSURE OF THE INVENTION

In order to solve these disadvantages, an object of the presentinvention is to provide a manufacturing method in which a green compactis having a through-hole or an undercut part can be easily manufacturedwithout causing breakage.

Another object of the present invention is to provide a manufacturingdevice appropriate for the manufacturing method of the green compacthaving the through-hole or the undercut part.

To achieve these objects, the manufacturing method of the green compactaccording to the present invention is characterized in that it comprisesa step of filling material powder into a cavity formed of a die havingin a vertical direction a die hole in a shape matching a contour of thegreen compact including a through-hole at a part connected continuouslyto a base part and a lower punch inserted into the die hole from theunderside of the die, a step of obtaining a preform by temporarilycompressing the material powder filled in the cavity by means of anupper punch inserted from the upside of the die into the die hole andthe lower punch, a step of punching out a shape of the through-hole byinserting a punch-out pin having a shape corresponding to across-section of the through-hole into the preform, a step of obtaininga green compact by pressurizing and compressing the preform by means ofboth of the upper and lower punches in a state in which the punch-outpin is being inserted, a step of pulling out the punch-out pin from thegreen compact, and a step of taking out the green compact from thecavity.

According to the manufacturing method of the present invention, thelower punch is first inserted into the die hole from the underside ofthe die so that the cavity is formed of the lower punch and the diehole.

The material powder is then filled in the cavity. When the materialpowder is filled, the upper punch is inserted into the die hole from theupside of the die and the material powder is temporarily compressedbetween the upper and lower punches so that the preform is obtained. Onthis occasion, since a core is not disposed in the cavity, the materialpowder can be filled at uniform density.

The punch-out pin is then inserted into the preform. On this occasion,since the material powder is temporarily compressed as described above,the shape of the through-hole can be easily punched out by the punch-outpin.

Thereafter, the preform is pressurized and compressed by both of theupper and lower punches while the punch-out pin is being inserted intothe preform. As the punch-out pin works as a core, the green compacthaving the through-hole in a shape matching the contour of the punch-outpin is obtained. The preform is obtained by temporarily compressing thematerial powder which is filled at the uniform density. Therefore, byfurther pressurizing and compressing the preform, a possibility that thematerial powder upper than the punch-out pin and that lower than thepunch-out pin have different density can be prevented even if thepunch-out pin is being inserted.

The punch-out pin is then pulled out from the obtained green compact andthe green compact is taken out so that a completed product can beobtained.

The manufacturing method of the green compact according to the presentinvention is also characterized in that it further comprises a step ofsintering the green compact taken out from the cavity and a step offorming a pair of leg parts connected continuously at the base part andan undercut part formed between both of the leg parts by cutting off apart of a peripheral wall which forms the through-hole of the sinteredcompact.

Although a thin part is formed around the through-hole of the taken-outgreen compact, the thin part itself is the peripheral wall of thethrough-hole and connected at a part facing the base part, and therebydeformation is limited in the sintering and warpage or the like can besecurely prevented from occurring.

Thus, the green compact having the pair of leg parts connectedcontinuously at the base part and the undercut part formed between bothof the leg parts can be obtained by sintering the taken-out greencompact and thereafter, cutting off the part of the peripheral wallwhich forms the through-hole.

If the pair of leg parts are wished to be parallel to each other whenthe green compact having the leg parts and the undercut part is formed,the through-hole is made to have a pair of parallel parts extending fromthe base part, a part of the through-hole facing the base part is cutoff, and thereby, a second sintered compact having a pair of parallelleg parts connected continuously at the base part can be formed.According to the manufacturing method of the present invention, sincethe deformation such as the warpage or the like does not occur in thethin part around the through-hole in the sintering described above, anexcellent parallel state can be given to the leg parts.

Further, the manufacturing method of this invention is characterized inthat it comprises a step of retracting and storing the material powder,which is punched out in said step of punching out a shape of saidthrough-hole by inserting a punch-out pin into said preform, outward ofthe cavity; a step of refilling the stored material powder into saidthrough-hole from which said punch-out pin has been pulled out in saidstep of pulling out the punch-out pin from the green compact; and a stepof removing the material powder refilled into said through-hole aftersaid step of taking out said green compact from said cavity.

In this manufacturing method, if the through-hole is kept as a hollowafter the punch-out pin is pulled out from the green compact obtained byfurther pressurizing and compressing the preform, the thin part maybreak when the green compact is taken out Therefore, when the punch-outpin is inserted into the preform to punch out the shape of thethrough-hole, the punched-out material powder is retracted to theoutside of the cavity by the punch-out pin and stored. At the time whenthe punch-out pin is pulled out from the green compact obtained by thepressurization and compression, the material powder retracted asdescribed above is refilled into the through-hole from which thepunch-out pin has been pulled out. Since the retracted material powderis temporarily compressed as described above, it can be refilled intothe through-hole easily without losing its shape.

When the green compact is taken out thereafter, the green compact can betaken out without causing breakage because its thin part is reinforcedby the material powder filled in the through-hole. The taken-out greencompact can then become a complete product by removing the materialpowder refilled in the through-hole.

The material powder punched out as described above may be collected andrecycled instead of being refilled into the through-hole.

The manufacturing method according to the present invention in which thepunched-out material powder is refilled into the through-hole asdescribed above can be realized more advantageously by a device formanufacturing the green compact, comprising:

a die having in a vertical direction a die hole in a shape matching acontour of the green compact including a through-hole at a partconnected continuously to a base part;

the lower punch inserted from an underside of the die into the die holeand forming a cavity to be filled with the material powder together withthe die;

an upper punch inserted from an upside of the die into the die hole andpressurizing and compressing the material powder filled in the cavitytogether with the lower punch;

a punch-out pin having a sectional shape corresponding to across-section of the through-hole, provided in the die to face thecavity, and inserted into a preform formed by temporarily compressingthe material powder by means of both of the upper and lower punches topunch out a shape of the through-hole; and

a refill pin having a sectional shape corresponding to the cross-sectionof the through-hole, provided in the die to face the cavity and thepunch-out pin, moving backward in synchronization with forward movementof the punch-out pin when the punch-out pin is inserted into thepreform, and moving forward in synchronization with backward movement ofthe punch-out pin when the punch-out pin is pulled out from the preformto refill the material powder into the through-hole.

According to the manufacturing device of the present invention, when thepunch-out pin is inserted into the preform to punch out the shape of thethrough-hole, the refill pin provided to face the punch-out pin movesbackward in synchronization with the forward movement of the punch-outpin. As the result, the material powder in the shape of the through-holewhich has been punched out by the punch-out pin is sandwiched betweenthe punch-out pin and the refill pin, retracted to a position where therefill pin has been before moving backward, and stored as it is.

Then, when the punch-out pin is pulled out from the preform, the refillpin moves forward in synchronization with the backward movement of thepunch-out pin. As the result, the material powder stored in the positionwhere the refill pin has been before moving backward moves while beingsandwiched between the punch-out pin and the refill pin so as to berefilled into the through-hole.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIGS. 1(a) and 1(b) are perspective views showing examples of a greencompact;

FIGS. 2(a) to 2(f) are explanatory cross-sectional views showing amanufacturing device and a manufacturing method of the green compactshown in FIGS. 1(a) and 1(b);

FIGS. 3(a) and 3(b) are perspective views showing another example of thegreen compact;

FIG. 4 is a cross-sectional view taken along a line IV—IV in FIG. 3(b);and

FIG. 5 is a cross-sectional view taken along a line V—V in FIG. 2(a).

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter embodiments according to the present invention will beexplained in detail with reference to the attached drawings.

First of all, a case of manufacturing a green compact in a shape shownin FIG. 1(a) or FIG. 1(b) will be explained as an example of a firstembodiment of the present invention.

The P/M products shown in FIG. 1(a) and FIG. 1(b) are used as machineparts as described above, the product in FIG. 1(a) comprises a rack 2provided at an end of a base part 1 and an axis hole 3 formed bypenetrating a part connected continuously to the base part 1, and theproduct in FIG. 1(b) comprises a hook part 5 provided at an end of anarm 4 extending from the base part 1 and the axis hole 3 formed bypenetrating the part connected continuously to the base part 1.

In this embodiment, as shown in FIG. 2(a), a device used formanufacturing the green compact shown in FIGS. 1 comprises a die 12having a die hole 11 in a vertical direction, a lower punch 13 insertedfrom the underside of the die 12 into the die hole 11, and an upperpunch 14 inserted from the upside of the die 12 into the die hole 11.Both of the punches are provided to ascend and descend freely.

The die hole 11 has a shape matching the vertical contour of the greencompact when the axis hole 3 of the green compact shown in FIG. 1 isdisposed horizontally. In the die 12, a punch-out pin 15 a and a refillpin 15 b in a shape corresponding to a cross-section of the axis hole 3are provided to face the die hole 11, opposing to each other.

In this device, the die 12, the lower punch 13, the upper punch 14, thepunch-out pin 15 a, and the refill pin 15 b are controlled by anot-shown controller. A microcomputer including CPU, RAM, ROM, and thelike is utilized as the controller.

Next, a manufacturing method of this embodiment will be explained withreference to FIG. 2(a) to FIG. 2(f).

As shown in FIG. 2(a), an upper surface of the lower punch 13 ispositioned at a lower part in the die hole 11 of the die 12 therebyforming a cavity 16 of the die hole 11 and the lower punch 13. On thisoccasion, the upper punch 14 is kept on standby above the die hole 11and the punch-out pin 15 a and the refill pin 15 b are kept on standbyat positions in which their ends face the die hole 11.

The cavity 16 is then filled with material powder 17 by a not-shownfeeder. Powder of ferrous metals and the like can be utilized as thematerial powder 17.

Thereafter, as shown in FIG. 2(b), the upper punch 14 descends andtemporarily compresses the material powder 17 which is filled in thecavity 16 between the upper punch 14 and the lower punch 13 so as toform a preform 18. Such a degree of the temporary compression that thematerial powder 17 can be maintained in the shape of the preform 18 isenough, and excessive compression is not necessary. The temporarycompression is generally carried out to compress the material powder 17by 20 to 30%.

Then, as shown in FIG. 2(e), the punch-out pin 15 a is inserted into thepreform 18 to punch out a shape of the axis hole 3. The refill pin 15 bmoves backward in synchronization with the forward movement of thepunch-out pin 15 a. As the result, the punch-out pin 15 a is inserted toa part in the die 12 where the refill pin 15 b has been disposed. Thematerial powder 17 (a part of the preform 18) punched out of the preform18 by the punch-out pin 15 a is retracted to a part in the die 12, wherethe refill pin 15 b has been moved backward, while the material powder17 is being sandwiched between the punch-out pin 15 a and the refill pin15 b. The material powder 17 is stored in the die 12.

The preform 18 is then pressurized and compressed between the upperpunch 14 and the lower punch 13 while the punch-out pin 15 a is beinginserted therein as shown in FIG. 2(d), so as to finally form a greencompact 19 having the shape shown in FIG. 1(a) or FIG. 1(b).

Subsequently, the punch-out pin 15 a is pulled out from the greencompact 19 as shown in FIG. 2(e). On this occasion, if the die 12 andthe upper punch 14 are slightly raised in advance, an inner stresscaused in the green compact 19 by the pressurization and compression isreleased, which allows the punch-out pin 15 a to be pulled out easily.

When the punch-out pin 15 a moves backward, in synchronization with thebackward movement, the refill pin 15 b moves forward. The ends of thepunch-out pin 15 a and the refill pin 15 b are returned to the state inwhich they face the die hole 11 as shown in FIG. 2(e).

As the result, the material powder 17 which has been stored in the die12 while being sandwiched between the punch-out pin 15 a and the refillpin 15 b is pushed by the refill pin 15 b to be refilled into the axishole 3 of the green compact 19.

Then, as shown in FIG. 2(f), the die 12 descends while the green compact19 is being lightly sandwiched between the upper punch 14 and the lowerpunch 13 to knock out the green compact 19 and the upper punch 14ascends and moves to the upper part of the die hole 11 so that the greencompact 19 is released.

Since the temporarily compressed powder material 17 is refilled into theaxis hole 3, the thin part of the base part 1 of the green compact 19 isreinforced. Therefore, even if the green compact is released asdescribed above, breakage is not caused in the thin part and a productin a complete shape can be obtained.

After being taken out from the die, the green compact 19 can be madeinto the shape shown in FIG. 1(a) or FIG. 1(b) by removing the powdermaterial 17 refilled into the axis hole 3 and sintering the greencompact 19. Since the powder material 17 is not integrated with thegreen compact 19 but only filled in the axis hole 3, it can be removedeasily by air blowing or the like.

Subsequently, a case of manufacturing P/M product in a shape shown inFIG. 3(a) will be explained as a second embodiment according to thepresent invention. The product shown in FIG. 3(a) is utilized as amachine part as described above, composed of a hook part 22 provided atthe front end of a rod part 21 and a pair of parallel leg parts 24, 24connected continuously at abase part 23 which is the rear end of the rodpart 21, and has an undercut part 25 between the leg parts 24, 24 asdescribed above.

In order to get the product in a shape shown in FIG. 3(a) in thisembodiment, a green compact shown in FIG. 3(b) is first manufactured.The green compact shown in FIG. 3(b) is so structured that the leg parts24, 24 are connected at a connection part 26 provided at a part facingthe base part 23, and the undercut part 25 shown in FIG. 3(a) is variedto a through-hole 25 a surrounded by the leg parts 24, 24 and theconnection part 26. As the result, the through-hole 25 a is connectedcontinuously to the base part 23 and has a shape including the parallelparts 24, 24 extending from the base part 23.

Since the green compact shown in FIG. 3(b) has the same structure asthat of the green compact shown in FIG. 1(a) and FIG. 1(b) except thatthe axis hole 3 is varied to the through-hole 25, it can be formed inthe same method as that of the aforesaid first embodiment, in accordancewith the steps in FIG. 2(a) to FIG. 2(f).

In this embodiment, a thin part around the through-hole 25 a(specifically, the leg part 24 in FIG. 3(b)) of the green compact 19shown in FIG. 2(f) is reinforced because the temporarily compressedpowder material 17 is refilled into the through-hole 25 a. Accordingly,even if the green compact is taken out in the aforesaid releasing way,the thin leg part 24 does not break.

After the green compact 19 is taken out, it can be made into the shapein FIG. 3(b) by removing the powder material 17 refilled into thethrough-hole 25 a Since the powder material 17 is not integrated withthe green compact 19 but only filled in the through-hole 25 a, it can beremoved easily by air blowing or the like.

Then, by sintering the green compact 19, a compacted body in which thepowder material 17 is mutually combined can be obtained. The leg parts24, 24 are connected by the connection part 26 and an excellent parallelstate can thus be obtained without causing deformation such as warpagein the sintering.

Thereafter, the sintered compact 19 is cut at the position of a virtualline shown in FIG. 4 to cut off the connection part 26. As the result, aside of the through-hole 25 a which faces the base part 23 is opened sothat, as shown in FIG. 3(a), a desired product (a second sinteredproduct) comprising a pair of parallel leg parts 24, 24 connectedcontinuously at the base part and having the undercut part 25 formedbetween the leg parts 24, 24 can be obtained.

Since only the connection part 26 is cut off, the undercut part 25 canbe formed much more easily than in the case of performing cutting workand the like on a massive green compact. The cut-off of the connectionpart 26 can be performed by a device which is generally known by itself

Although the through-hole 25 a has the shape including the parallelparts 24, 24 extending form the base part 23 in this embodiment, theshape of the through-hole 25 a is not limited to this, and the pair ofleg parts 24, 24 of the green compact are not limited to the parallelones.

In each of the embodiments, as shown in FIG. 2(a) to FIG. 2(f), thelower punch 13 and the upper punch 14 are explained as singular punches,but the lower punch 13 and the upper punch 14 may be divided intoseveral parts corresponding to the shape of the green compact. Forexample, in a case of shaping the green compact shown in FIG. 3(b), theconnection part 26 of the green compact shown in FIG. 3(b) is formed bya lower punch 13 a and an upper punch 14 a, the leg part 24 is formed bya lower punch 13 b and an upper punch 14 b, and the rod part 21including the not-shown hook part 22 is formed by a lower punch 13 c andan upper punch 14 c as shown in FIG. 5. Each of the punches is providedto ascend and descend freely and independently.

Furthermore, in each of the embodiments, when the punch-out pin 15 a isinserted into the preform 18 to punch out the shape of the axis hole 3or the through-hole 25 a, the punched-out material powder 17 is storedin the die 12, and when the punch-out pin 15 a is pulled out, thematerial powder 17 is refilled into the axis hole 3 or the through-hole25 a. However, it is not always necessary for the punched-out materialpowder 17 to be refilled into the axis hole 3 or the through-hole 25 aand, for example, the punched-out material powder 17 may be fallen intoand collected in a hollow which is provided in the die 12. The collectedmaterial powder 17 can thereby be recycled.

INDUSTRIAL APPLICABILITY

The present invention can be utilized for manufacturing a green compacthaving a through-hole or an undercut part.

What is claimed is:
 1. A method for manufacturing a green compact,comprising: a step of filling material powder into a cavity formed of adie having in a vertical direction a die hole in a shape matching acontour of said green compact including a through-hole at a partconnected continuously to a base part and a lower punch inserted from anunderside of said die into said die hole; a step of obtaining a preformby temporarily compressing the material powder filled in said cavity bymeans of an upper punch inserted from an upside of said die into saiddie hole and said lower punch; a step of punching out a shape of saidthrough-hole by inserting a punch-out pin having a shape correspondingto a cross-section of said through-hole into said preform; a step ofobtaining said green compact by pressurizing and compressing saidpreform by means of both of said upper and lower punches in a state inwhich said punch-out pin is being inserted; a step of pulling out saidpunch-out pin from said green compact; and a step of taking out saidgreen compact from said cavity.
 2. A method for manufacturing a greencompact according to claim 1, further comprising: a step of sinteringsaid green compact taken out from said cavity; and a step of forming apair of leg parts connected continuously at said base part and anundercut part formed between both of said leg parts by cutting off apart of a peripheral wall forming said through-hole of said sinteredcompact.
 3. A method for manufacturing a green compact according toclaim 2, wherein said through-hole includes a pair of parallel partsextending from said base part, said step of forming a pair of parallelleg parts connected continuously at said base part and an undercut partformed between both of said leg parts is performed by cutting off a partfacing said base part from the peripheral wall which forms saidthrough-hole.
 4. A method for manufacturing a green compact according toany one of claim 1 to claim 3, further comprising: a step of retractingand storing the material powder, which is punched out in said step ofpunching out a shape of said through-hole by inserting a punch-out pininto said preform, outward of the cavity; a step of refilling the storedmaterial powder into said through-hole from which said punch-out pin hasbeen pulled out in said step of pulling out the punch-out pin from thegreen compact; and a step of removing the material powder refilled intosaid through-hole after said step of taking out said green compact fromsaid cavity.
 5. A device for manufacturing a green compact, comprising:a die having in a vertical direction a die hole in a shape matching acontour of the green compact including a through-hole at a partconnected continuously to abase part; a lower punch inserted from anunderside of said die into said die hole and forming a cavity to befilled with material powder together with said die, an upper punchinserted from an upside of said die into said die hole and pressurizingand compressing the material powder filled in said cavity together withsaid lower punch; a punch-out pin having a sectional shape correspondingto a cross-section of said through-hole, provided in said die to facesaid cavity, and inserted into a preform formed by temporarilycompressing the material powder by means of both of said upper and lowerpunches to punch out a shape of said through-hole; and a refill pinhaving a sectional shape corresponding to the cross-section of saidthrough-hole, provided in said die to face said cavity and to face saidpunch-out pin, moving backward in synchronization with forward movementof said punch-out pin when said punch-out pin is inserted into thepreform, and moving forward in synchronization with backward movement ofsaid punch-out pin when said punch-out pin is pulled out from thepreform to refill the material powder into said through-hole.